Total knee arthroplasty is an effective operation. Post-surgery rehabilitation, based on early and intensive progressive exercise programs, plays a substantial role and telerehabilitation can be an effective safe option. This retrospective study aimed to compare traditional in-presence rehabilitation and telerehabilitation for total knee arthroplasty, based on our experience during the Italian COVID-19 lockdown. We retrospectively analyzed 164 patients (94 females and 70 males) enrolled in 2020 within 2 weeks after total knee replacement to perform post-operative outpatient rehabilitation. The clinical results of 82 patients (mean age 66.8 ± 10.2 years) performing telerehabilitation with those obtained from a similar cohort of 82 patients (mean age 65.4 ± 11.8 years) performing traditional in-presence outpatient rehabilitation were compared. Clinical outcomes were examined by comparing the gait speed (Time Up and Go-TUG test), the range of motion, the pain intensity (VAS), the functional status (Oxford Knee Score-OKS and Knee injury and Osteoarthritis Outcome Score-KOOS) and the overall satisfaction (Self-administered patient satisfaction scale) 12 weeks after the beginning of the physiotherapeutic protocol. Telerehabilitation was non-inferior to traditional in-presence rehabilitation in all of the investigated areas and no statistical difference in terms of effectiveness was detected at 12 weeks, as confirmed by the respective patient-reported outcome scores such as TUG test (reduced from 20 ± 2 s to 12 ± 1.5 s for the telerehab cohort and from 18 ± 1.5 s to 13.1 ± 2 s for the in-presence rehabilitation one), pain VAS, OKS (improved from 22 ± 1.3 to 36 ± 2.7 for the telerehab cohort and from 23 ± 2.1 to 35.1 ± 4.2 for the in-presence group), KOOS (improved from 46.2 ± 10.2 to 67.4 ± 3.8 for the telerehabilitation cohort and from 48.4 ± 8.4 to 68.3 ± 6.6 for the other group), and the Self-administered patient satisfaction scale (more than two-thirds of patients globally satisfied with the results of their surgery in both groups). The telerehabilitation program was effective after total knee replacement and yielded clinical outcomes that were not inferior to conventional outpatient protocols.